Process for improving the strength of wool or silk fibers and products thereof



United States Patent 3,479,128 PROCESS FOR IMPROVING THE STRENGTH OFWOOL OR SILK FIBERS AND PRODUCTS THEREOF Peter Jof chen Borchert, Elkhart, Ind., assignor to Miles Laboratories, Inc., Elkhart, Ind., a corporation of Indiana No Drawing. Filed Dec. 27, 1965, Ser. No. 516,659 Int. Cl. D06m 15/04 U.S. Cl. 8-127.6 6 Claims ABSTRACT OF THE DISCLOSURE The tensile strength of wool and silk fibers can be increased by treating such fibers with an aqueous dispersion of a dialdehyde polysaccharide.

This invention relates to proteinaceous natural fibers having improved tensile strength. More particularly, it relates to wool or silk fibers which have been treated with an aqueous dispersion of a dialdehyde polysaccharide, said treated fibers having improved tensile strength as compared to untreated fibers.

Natural proteinaceous fibers, and especially wool and silk fibers, are widely used in the textile industry. Wool, for example, is valued for the warmth, resilience and crease and crush resistance of its fabrics. Its average tensile strength, however, is quite low and wool fabrics are therefore easily deteriorated when subjected to localized physical force. Wool is also subject to attack by bacterial action or by chemicals, such as acids, which weaken its strength. Silk is known to have a natural tensile strength higher than that of wool, but it is still desired to improve the strength of silk so as to be more competitive with synthetic fibers of high strength.

It is an object of the present invention to provide natural proteinaceous fibers having improved tensile strength.

It is another object of the present invention to provide natural proteinaceous fibers which are more resistant to attack by bacterial action or by chemical action.

It is a further object to provide a process-.for treating natural proteinaceous fibers to improve their tensile strength.

In accordance with the present invention a process is provided which comprises contacting a natural proteinaceous fiber, such as wool or silk, with an aqueous dispersion of a dialdehyde polysaccharide and forming a fiber dialdehyde polysaccharide raection product. The concentration of the dialdehyde polysaccharide in the aqueous dispersions useful in the present invention is from about 0.1 to about 10 weight percent based on the total weight of the dialdehyde polysaccharide and water. Preferably, the concentration is from about 0.15 to about weight percent.

These dispersions can be prepared by cooking the dialdehyde polysaccharide in water to rupture the granules of the dialdehyde polysaccharide. The cook is generally considered to be complete when no unruptered granules are found to be present. This can be ascertained, if desired, by means of centrifugation or by other appropriate analytical means. Sometimes the dispersion of the dialdehyde polysaccharide can be facilitated by the use of a small amount of a buffer salt, such as sodium acetate, sodium citrate, rnonosodium phosphate, borax or sodium hexametaphosphate. In general, the amount of buffer salt used should be inthe range of from about 0.1 to about 5 weight percent based on the weight of the dialdehyde polysaccharide used. The dispersion temperature is generally from about 60 C. to about 95 C.

Following the step of dispersing the dialdehyde poly- 3,479,128 Patented Nov. 18, 1969 saccharide in water, the pH of the resulting dispersion, if not already in the range of from about 2 to about 7, is adjusted to a value within this range by the addition of a suitable reagent, such as sulfuric acid to lower the pH or sodium hydroxide to increase the pH. A dispersion pH within this range prevents alkaline degradation of the dialdehyde polysaccharide and provides an improved reaction bond between the dialdehyde polysaccharide and the wool or silk fibers.

Following adjustment of the pH of the aqueous dialdehyde polysaccharide dispersion, such dispersion is then brought into contact with the wool or silk fibers to provide a reaction therebetween. Such reaction takes place at a temperature from about 20 C. to about 40 C. for from about 5 minutes to about 60 minutes.

After treatment with the aqueous dialdehyde polysaccharide dispersion, the wool or silk fibers are then washed with water at room temperature (about 20 C.- 25 C.) and then dried at room temperature. The resulting fibers can then be employed in the production of textiles having improved strength.

The present invention also has other advantages. Wool is subject to deterioration caused by physical force, bacterial action or chemical action. If partially deteriorated wool is treated with an aqueous dispersion of dialdehyde polysaccharide according to the present invention some of the fiber strength can be restored.

It has also been found that wool treated in accordance with the present novel process has improved resistance to deterioration by bacterial or chemical action.

The dialdehyde polysaccharides utilized in the process of this invention are well known in the art. Such materials are frequently referred to as periodate oxidized polysaccharides because of their preparation by the well known oxidation of polysaccharides with periodic acid. This preparation can be illustrated by the conversion of a polysaccharide, such as starch, to dialdehyde starch or periodate oxidized starch using periodic acid in accordance with the following equation:

H OH

CHzOH H i H 1 H I H103 H2O C-C II H O O I:

wherein n stands for the number of repeating structural units in the molecule, which may range from as few as about 20 to as many as several thousand. The preparation of dialdehyde starch is more particularly described in U.S. Patent Nos. 2,648,629 of W. Dvonch et al. and 2,713,553 of C. L. Mehltretter.

The dialdehyde polysaccharides to be used in preparing the novel reaction products of the present invention may be the dialdehyde derivatives of any polysaccharide, such as corn, wheat, rice, tapioca or potato starches, amyloses, amylopectins, celluloses, gums, dextrans, algins, inulins and the like. Of these polysaccharides, the dialdehyde derivatives of starch, known generically as dialdehyde starch, are the best known and most widely used. However, where it is desired to have dialdehydes of other polysaccharides, these may be used as well. The dialdehyde polysaccharides useful in the present invention can contain from about 0.5 to about 100 mole percent dialdehyde polysaccharide units. In general, it is preferred to use dialdehyde polysaccharides which are about 90 to 100 percent oxidized, i.e., those wherein about 90 to 100 Co. The three strands were then washed three times with water and then treated as follows:

Strand (1) was soaked for 30 minutes at 25 C. in an aqueous dispersion containing 0.5 weight percent dialdehyde starch having a pH of 5.8.

out of each 100 of the original anhydr-oglucose units have 5 Strand (2) was soaked for 30 minutes at 25 C. in an been converted to dialdehyde units such as by periodate aqueous dispersion containing 1.0 weight percent dialdeoxidation as above described. hyde starch having a pH of 5.8.

It is not known exactly how the dialdehyde polysac- Strand (3) was soaked for 30 minutes at 25 C. in charide reacts with the wool or silk fibers so as to increase distilled water having a pH adjusted to 5.8. the fiber tensile strength. Natural proteinaceous fibers, All the strands were then removed from the solutions, such as wool or silk, are formed from polypeptide chains washed twice with distilled water and then heated to 100 containing reactive groups such as free amino groups and C. for 3 minutes. The strands were washed again with free -SH groups in such chains. The dialdehyde polysacdistilled water and then wiped dry with a towel. Further charide can possibly react with such groups to form crossdrying was carried out at room temperature for 5 hours. linking bonds between such reactive groups of adjacent Between 10l2 single fibers were then isolated from each polypeptide chains and thus increase the internal strength strand and were tested for tensile strength using comof each of the fibers which are composed of multiple monly available testing apparatus. polypeptide chains. The following tests results were obtained: It can be readily shown that the dialdehyde polysac- TABLE 1 charide is retained on the wool or silkfibers after reacting therewith. Even though some of the carbonyl groups 3333 of the dialdehyde polysaccharide react with the fibers, Ave age Increase 'there are still some unreacted aldehyde groups remaining 5333 fifgf These unreacted aldehyde groups within the fibrous poly- Treating Solution percent mer chain are available to undergo well known reactions Water (Control) @361 with aldehyde reagents. Colored dye staining reagents, dialdehyde Starch 0-425 such as the sulfurous acid solution of the disodium salt 10% dialdehyde Starch 0'402 of the trisulfonic acid of rosaniline (Fuchsin solution) It can be readfl y seen from the above data that treating y? been found extremely liseful m quahtatwely a natural proteinaceous fiber, such as wool, with an aqueminlng the presence of the dialdehyde polysaccharlde. If

ous dispersion of a dialdehyde starch remarkably inan untreated wool or silk fiber is contacted with the h t th f th t t d fib It v 1 o Fuchsin solution, a bright red color is developed after creases t e tensl e S rang 0 e rea e was a S found that the treated fibers were more resistant to deteabout 20 mlnutes. In contrast to this, a wool or s1lk fiber treated with a dialdeh de 01 Sacch rid d v 10 S (166 r1orat1on from bacterial actlon and chemical action the p y a e e p a p the untreated fibers blue-reddish color wlthm only about 1-5 mlnutes after contacting Fuchsin solution. This fast color development EXAMPLE 2 is due to reaction between free aldehyde groups of the dialdehyde polysaccharide retained by the fiber and the aqueous dlsperslon contammg 9' Yvelght percent Fuchsin Solution. 40 dlaldehyde starch, prepared as described in Example 1, The invention will be further described in the following was dlvldfad Into The PH values of these examples. four portions were ad usted to 3.6, 5.1, 6.7 and 7.4, re-

spectlvely. Four strands of defatted sheep wool, each EXAMPLE 1 weighing 1 g., were separately soaked in 200 m1. portions of the above aqueous dispersions for 30 minutes A 176 g. quantity of dialdehyde corn starch being about at 25 C. A fifth strand of sheep wool was soaked in 95 percent oxidized was added to an aqueous solution of distilled water for 30' minutes at 25 C. and pH 6.2. The 4.4 g. borax and 1600 ml. of distilled water at 65 C. strands were then removed from the solutions, washed The mixture was mechanically stirred for 55 minutes twice with distilled water and allowed to dry at room while maintaining the mixture temperature at 65 C.70 temperature for 5 hours. Individual fibers from each C. During this time the dialdehyde corn starch was substrand were then tested for tensile strength. stantially completely dispersed. A 0.1 g. quantity of a Fibers from each strand were also subjected to a siliceous filter aid was added to the dispersion and the Fuchsin Test. A 0.5 g. quantity of Fuchsin acid (dimixture was filtered warm through a vacuum filter. The sodium salt of the tn'sulfonic acid of rosaniline) was disfiltrate was an aqueous dispersion of 10 weight percent solved in 500 ml. of distilled water at C. The deep dialdehyde starch. It was then cooled to room temperareddish solution was decolorized by saturating the soluture and divided into three portions. Such portions were tion with sulfur dioxide. A second solution consisting of then diluted with appropriate quantities of distilled water 50 weight percent dilute sulfurous acid was also prepared. to form dispersions having dialdehyde starch concentra- Before use a mixture was prepared consisting of 3 parts tions of 0.25 weight percent, 0.5 weight percent, and 1.0 60 by volume Fuchsin solution and 1 part "by volume of the weight percent, respectively. sulfurous acid solution. The fiber to be tested was dipped Three strands of defa-tted sheep wool were soaked for in such mixture for 3-20' minutes. Wool fiber treated with two hours at room temperature (about 20 C.25 C.) dispersions of dialdehyde starch generally develops a in distilled water containing 6 drops/liter of an anionic deep-blue-reddish color within 3-10 minutes, while unsurfactant. This surfactant is marketed under the trade treated fiber develops a red color after about 20 minutes. name of Tergitol Anionic 4 by Union Carbide Chemicals The test results are shown below:

' TABLE 2 Treating Tensile Solution Average Increase (Wt. percent Treating Tensile Over dialdehyde Solution, Strength Control, Fuehsin starch) pH (lbs) percent Test 6. 2 0.310 Red eolor after 20 min. 3.6 0.435 40.3 Blue-red color in 3-5 min. 5. 1 0.347 11.9 Blue-red color in 10 min. 6. 7 0. 445 43. 6 Blue-red color in 3-5 min. 7.4 0.807 Red color in 20 min.

It can be seen from the the above data that aqueous dispersions of dialdehyde starch having pH values in the range from 2 to 7 can be employed to react with wool fibers to increase the tensile strength of the wool fibers. It can also be seen that the dialdehyde starch is retained on the treated fibers as indicated by the Fuchsin Test.

While the above disclosure is directed primarily at treating wool with dialdehyde corn starch, it should be understood that silk and other dialdehyde polysaccharides can be employed in accordance with the present invention.

in summary, the present invention involves treating wool or silk fibers with an aqueous dispersion of a dialdehyde polysaccharide, such as dialdehyde starch, at a pH of from about 2 to about 7 to cause a reaction between the wool or silk fibers and the dialdehyde starch so as to increase the tensile strength of the fibers.

What is claimed is:

1. A process for improving the strength of Wool or silk fibers which comprises contacting the wool or silk fibers for from about 5 minutes to about 60 minutes at a temperature from about 20 C. to about 40 C. with an aqueous dispersion of a dialdehyde polysaccharide, said dispersion containing from about 0.1 to about 10 weight percent dialdehyde polysaccharide and having a pH value of from about 2 to about 7.

2. A process according to claim 1 wherein the dialdehyde polysaccharide is dialdehyde starch.

3. A process according to claim 1 wherein the fiber is wool.

4. A process according to claim 1 wherein the fiber is silk.

5. A process according to claim 1 wherein the aqueous dispersion of dialdehyde polysaccharide contains from about 0.15 to about 5 weight percent of a dialdehyde polysaccharide.

6. A fiber material having improved tensile strength consisting essentially of wool or silk fibers treated in accordance with the process of claim 1.

References Cited UNITED STATES PATENTS 3,093,439 6/1963 Bothwell 8127.6 X 3,165,375 1/1965 Tesoro 8127.6

RICHARD D. LOVERING, Primary Examiner U.S. Cl. X.R. 

